Pictures on social media showed a huge crowd blocking the path near the intersection with South Anne Street and Harry Street.
The protest started at the Custom House Quay before moving on to Grafton Street.
Gardaí said the protesters "dispersed without incident", while they will investigate the organisation of the protest.
A Garda spokesman said: "Gardaí attended the scene of a protest earlier today, Saturday, 3rd October, 2020, that commenced at Custom House Quay, North Dock, Dublin, and concluded at Grafton Street, Dublin 2, where all persons present dispersed without incident.
"An Garda Síochána has no role in permitting or authorising protest marches, there is no permit/authorisation required for such events. An Garda Síochána objective in relation to protests is the prevention of any Breach of the Peace and facilitate ongoing business continuity around the protest event.
"The Health Act 1947 (Section 31A-Temporary Restrictions) (COVID-19) (No.5) Regulations 2020, as amended are currently in force, and place penal restrictions on persons organising certain events. An Garda Síochána will investigate the organisation of this event.
"Individual attendance, social distancing, wearing of masks in public area and other such public health guidelines are not penal regulations.
"In supporting the COVID-19 public health guidelines and regulations, An Garda Síochána has and will continue to adopt, a graduated policing response based on its tradition of policing by consent. This has seen Garda members engage, educate, encourage and, as a last resort, enforce. Where potential breaches of the Public Health Regulations are identified a file is submitted to the Director of Public Prosecutions for a direction as to how to proceed."
